Re: [RFC/PATCH 0/4] CPUSET driven CPU isolation

Max Krasnyanskiy
2008-02-28T17:48:23Z

Ingo Molnar wrote:
> * Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
>
>> My vision on the direction we should take wrt cpu isolation.
>>
>> Next on the list would be figuring out a nice solution to the
>> workqueue flush issue.
>
> nice work Peter, i find this "system sets" extension to cpusets a much
> more elegant (and much more future-proof) solution than the proposed
> spreadout of the limited hack of isolcpus/cpu_isolated_map. It
> concentrates us on a single API and on a single mechanism to handle
> isolation matters. (be that for clustering/supercomputing or real-time
> purposes)
Come on Ingo. You make it sounds like it's radically different solution.
At the end of the day we have a bitmap that represents which CPUs can be used
for the kernel stuff. How is that different ?
I was saying all along that cpusets is a higher level API and was discussing
or trying to discuss (people were ignoring my questions) ways to integrate it.

> Thanks for insisting on using cpusets for this!
>
> i've queued up your patches in sched-devel.git, and lets make sure this
> has no side-effects on existing functionality. (it shouldnt)
Hmm, that was easy. Not a single ack. Even the core part is not complete yet.
I pointed out several issues. Like the fact that it does not provide full
isolation because it does not move timers, does not handle workqueues.
I did not even get a chance to test this stuff properly and see if it actually
solves the usecase I was solving with my patches.
_Obviously_ we could not have taken my tested solution and evolved it in the
direction people wanted to see it evolve, ie integration with the cpusets :(.

My main concern is that it introduces a whole new set of notifiers that
perform similar functions to what CPU hotplut already does.

Max